/Engine/Source/Editor/UnrealEd/Classes/Editor/EditorEngine.h
Delegate called as each PIE instance login is complete, continues creating the PIE world for a single instance
virtual void OnLoginPIEComplete ( int32 LocalUserNum, bool bWasSuccessful, const [FString](API\Runtime\Core\Containers\FString) & ErrorString, [FPieLoginStruct](API\Editor\UnrealEd\FPieLoginStruct) DataStruct )